The Global Aerosol Cliatology Project (GACP) was established in 1998 as part of the NASA Radiation Sciences Program and the Global Energy and Water Cycle Experiment (GEWEX). Its main objectives have been to

1. Analyze satellite radiance measurements and field observations in order to infer the global distribution of aerosols, their properties, and their seasonal and interannual variations; and
2. Perform advanced global and regional modeling studies of the aerosol formation, processing, and transport.

To accomplish these objectives, the Earth Science Enterprise (formerly called Mission to Planet Earth) of NASA Headquarters had established a processing center at the NASA Goddard Institute for Space Studies and issued a research announcement (NRA-97-MTPE-16). The principal investigators of the successful proposals formed the GACP Science Team. Besides pursuing their individual research objectives, the members of the Science Team have participated in selecting candidate algorithms to be applied to the full period of satellite measurements in order to estimate parameters of significance to the aerosol climatology. The processing center has been employing the algorithms recommended by the Science Team to produce the satellite element of the combined GACP aerosol product.

A major outcome of this collective research effort is a 23-year global aerosol climatology compiled from channel-1 and -2 AVHRR data and supplemented by data from other satellites, field observations, and chemical-transport modeling. The resulting datasets and analysis products have been documents in numerous peer-reviewed publications, including a special issue of the Journal of Atmospheric Sciences. They have been used to improve the understanding and modeling of the climate forcing due to changing aerosols, including both the direct radiative forcing by the aerosols and the indirect radiative forcing caused by the effects of changing aerosols on cloud properties.

Hal Maring, Program Manager Radiation Sciences Program Sun-Earth System Division NASA Headquarters 300 E ST SW Washington DC 20546-0001 Phone: (202) 358-1679 Fax: (202) 358-2770 E-mail: hal.maring@nasa.gov		Paul D. Try, Director International Gewex Project Office 1010 Wayne Ave. Suite 450 Silver Spring, MD 20910 USA Phone: (301) 565-8345 Fax: (301) 565-8279 E-mail: gewex@gewex.org
Joyce E. Penner, Science Team Leader Dept. of Atmospheric, Oceanic and Space Sciences University of Michigan 2455 Hayward Street Ann Arbor, MI 48109-2143 Phone: (734) 936-0519 Fax: (734) 764-5137 E-mail: penner@umich.edu		Michael Mishchenko, Project Manager NASA Goddard Institute for Space Studies 2880 Broadway New York, NY 10025 Phone: (212) 678-5590 Fax: (212) 678-5552 E-mail: mmishchenko@giss.nasa.gov